73 E body front disc brakes conversion on A body. Where did I mess up?

Professor Fate said

Okay, we're not connecting here.
Swap the ball joint to the other spindle.
View attachment 1716338475
The "arm" of the ball joint will now be going under the caliper bracket, which is now facing the rear.
The "recess" is for the bolt head- no washers needed.

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That's exactly what I did. The recess, as I've said, prevents swapping the ball joint. If there were no recess, no problem. I like your graphics. Thanks for trying but the ball joints make it not possible. The recess is on both sides of the ball joint as well.